The role of trace reactive gases in regulating complex biological functions such as vasorelaxation, neurotransmission, and inflammation has received considerable attention in the biomedical research community, including the Nobel Prize in Medicine for research on the physiological significance of NO. Laboratory research into the role of this and other trace gases is presently constrained by the lack of reliable, versatile instrumentation for ppb-levels of biogenic gases. In a successful Phase I program, Physical Sciences Inc. (PSI), Rice University, and the Baylor College of Medicine showed that endogenous CO and NO production could be measured in atmospheres associated with cultured cells using room-temperature, quantum cascade laser-based absorption sensing. No presently available instrumentation is capable of multi-species, time-resolved measurements of these gases. In the proposed Phase II program, the team will develop prototype laboratory instruments for routine, automated and simultaneous detection of interrelated endogenous gases in biomedical laboratories. These instruments will be fully integrated and automatic sensors, including thermally-stabilized cultured cell vessels, compact optical absorption configurations, and software controlled data acquisition and reduction. Extensive test and evaluation by technicians in biomedical laboratories of participating institutions will be used to refine the instrument concept for subsequent marketing and sales.